A condensation reaction is a reaction for forming a new chemical bond between compounds while producing a low molecular weight substance such as water, and is frequently used in organic synthesis. However, generally, the condensation reaction is conducted using a solvent under an acid catalyst, and, according to circumstances, takes much time and requires high-temperature conditions.
In particular, in a condensation reaction in which water is produced, it is very possible to lose a functional group, such as an alkoxysilyl group, to be used in subsequent steps because water is prone to react with the functional group. In order to overcome the above problem, when a protecting group is used, a multistep reaction is adopted to have low yield, a major cause for economic inefficiency.
For example, in order to react (aminoalkyl)trialkoxysilane with dicarboxylic acid, first, dicarboxylic acid is converted into carboxylic acid chloride, and then the carboxylic acid chloride are reacted with (aminoalkyl)trialkoxysilane in the presence of triethylamine. However, such a reaction is problematic in the yield and reaction conditions are not definite [Xiang, S.; Zhang, Y.; Xin, Q.; Li, C. Angew. Chem. Int. Ed. 2002, 41(5), 821-824.], and a post-treatment process is very complicated [Katz, A.; Davis, M. E. Nature, 2000, 403, 286-289.].
Further, when a substrate, such as amino acid or hydrocarboxylic acid, is used, since the substrate has many functional groups, side reactions may occur due to the self-condensation of the functional groups. Therefore, it is required to introduce a protecting group, and reaction time and production costs are increased due to the increase in the preparative steps.
Accordingly, in recent years, in order to reduce the preparation steps and reaction time and to minimize the formation of volatile organic substances, research on novel synthetic methods which can maintain high yield and selectivity without using a solvent has been variously made.
Considering that environment friendliness and economical utilization of materials have been lately issued, such research on the new synthetic methods is very important. Among the new synthetic methods, a synthetic method using microwaves has lately attracted considerable attention.
A microwave, which is an electromagnetic wave having a frequency of 1˜300 GHz and a wavelength of 1 mm˜1 m, is called a decimeter wave, a centimeter wave or a millimeter wave.
One of the household electric appliances using a microwave is a microwave oven. The microwave oven increases the temperature of foods by applying an electromagnetic wave having a small length of 1˜2 mm to water present in the foods, thus causing water particles to collide with each other.
Such a microwave having various uses began to be applied to organic reactions in the mid-1980s. Thereafter, it was reported in several thousand theses that reaction rate was remarkably increased using the microwave [Lidstrom, P.; Tierney, J.; Wathey, B.; Westman, J. Tetrahedron 2001, 57, 9225-9283.; Lathed, M.; Hallberg, A. Drug Discovery Today 2001, 6, 406-416.].
The synthetic method using the microwave has well known advantages in that high yield can be obtained with little side products, reactants and solvents having low toxicity and reactivity are used, and experimental methods are simple. Thus, this method is chiefly used in environment-friendly organic reactions [Larhed, M.; Moberg, C.; Hallberg, A. Acc. Chem. Res. 2002, 35, 717-727.].
However, a conventional microwave reactor was problematic in that the wavelength of the microwave emitted therefrom was not constant, hot spots occurred, and safeness was not ensured, thereby decreasing reproducibility, but a recently developed microwave reactor overcame such problems to improve the reproducibility.
In many catalytic reactions, a catalytic reaction using a heterogeneous catalyst is advantageous in that a process for separating products may not be conducted for a long time and the recovery of the catalyst is easy, compared to a homogeneous catalytic reaction. Owing to these advantages of the heterogeneous catalyst, recently, many efforts to develop catalytic systems for asymmetric synthesis have been made.
As one of the efforts, in the case of asymmetric epoxidation, a polymer-supported catalytic system was developed using tartarate ester introduced into a polystyrene resin, but its chiral induction effect (about 50˜60%) was limited [Farrall, M. J.; Alexis, M.; Trecarten, M. Nouv. J. Chim. 1983, 7, 449.].
Further, when a polymer-supported catalytic system was developed using tartarate ester introduced into an inorganic material, the developed catalytic system had a problem of reproducibility [Choudary, B. M.; Valli, V. L. K.; Prasad, A. D. J. Chem. Soc. Chem. Commun. 1990, 1186. Baiker, A], and, when a polymer-supported catalytic system was developed using a gel-type polymeric ligand, the developed catalyst system had a problem of swelling during a reaction [Karjalainen, J. K.; Hormi, O. E. O.; Sherrington, D. C. Tetrahedron: Asymmetry 1998, 9, 2019.].
In order to solve the above problems, interest in the use of organic-inorganic hybrid materials has increased [Moreau, J. J. E.; Vellutini, L.; Man, M. W. C.; Bied, C. J. Am. Chem. Soc. 2001, 123, 1509-1510; Defreese, J. L.; Katz, A. Chem. Mater. 2005, 17, 6503-6506.].
Unlike organic polymers, the organic-inorganic hybrid materials do not swell or dissolve in organic solvents, and exhibit excellent mechanical and thermal stability.
Further, in the organic-inorganic hybrid materials, since their organic moieties are covalently bonded with inorganic materials, the possibility of leaching is decreased, and thus it is expected that the use of organic-inorganic hybrid materials will be expanded in the future.
Among these organic-inorganic hybrid materials, chiral catalytic materials having enantioselectivity particularly become the focus of attention, and it is very important to design and synthesize catalysts using chiral catalytic materials.
Considering the characteristics of the organic-inorganic hybrid materials and the chiral catalytic materials, in the present invention, it is determined that they can be easily changed such that they have functional groups serving to introduce amino acid, which can be coordinatively bonded with metals to have high enantiomeric purity, economic efficiency and catalytic activity, into inorganic materials.
Therefore, the present inventors have made efforts to overcome the disadvantages of the conventional synthetic methods, in that solvent and catalyst must be used, long reaction time is required, high-temperature conditions are required, and protecting groups must be used. As a result, we found a method of preparing a compound, in which an amino-acid derivative and aminoalkylsilane having an alkoxy group are condensed, using microwaves without solvent and catalyst for a short reaction time, high selectivity and high yield while maintaining the high reactivity of functional group. Based on these findings, the present invention was completed.